Schematic representation of aptamer-based biosensor for detection of AFB1. Cystamine (Cys) was immobilized on a gold electrode by chemisorption of thiols (1). Glutaraldehyde (GA) was added to the surface for linking covalently amino-groups of cystamine to amino-terminated dendrimers (2). PAMAM G4 dendrimers layer was reacted with NaBH4 for reducing the excess of GA (3). Next step includes addition of GA (4) that follows the anchoring of amino-modified aptamers and using NaBH4 for reducing the excess of GA (5). The sensor was ready for detection of AFB1 (6).